1. Field of the Invention
The present invention relates to a method for the ink jet recording and apparatus therefor, and particularly to purging bubbles off the ink flow path between the ink tank and the recording head of the apparatus.
2. Description of the Prior Art
Ink jet recording apparatus records letters or characters, graphic patterns, and the like, on a recording medium by jetting thereonto an ink in the form of droplets through slender nozzles. In order that the apparatus draws high-quality letters or charaters, graphic patterns, and the like the apparatus must be capable of performing a regular and intermittent jet of minute and equal-size ink droplets. For a smooth jet fly operation of such ink droplets and for stable drawing on a recording medium of letters or characters, graphic patterns, and the like, not only does the nature of the ink itself need to be sufficiently uniformly stable but the ink flow path between the ink tank and the recording head must be kept from the mixing thereinto of air bubbles.
Further, there often occurs clogging of the nozzles with solid matter produced in the ink, such as clots of the ink dried inside the nozzles, dust, paper dust, and the like, resulting in malfunction of the ink jet or unstable ink jet as well as in the lowering of the jetting capability such as the jet efficiency, the stability, responsiveness, etc., of the formation of ink droplets, and the like. Therefore it is necessary to get rid of such impurities as mentioned above.
As has been described, in the ink jet recording apparatus, it is indispensable to completely purge the ink flow path of the bubbles produced therein or solid matter that have mixed thereinto.
Where bubbles or foreign matter were present inside the nozzles of the recording head or inside the ink flow path, the following procedures have hitherto been taken:
(1) The ink tank is pressed partially to increase the ink pressure to thereby expel the bubbles, foreign matter, etc., together with the ink from the nozzles forming the tip of the ink flow path.
(2) A pressure chamber having an electrically driven pump or the like is provided in the middle of the ink supply system that connects the ink tank to the recording head to let the ink flow therethrough, and the ink with the flow quantity and pressure thereof increased by the pump is sent toward the nozzle side to thereby expel the bubbles, foreign matter, etc., from the nozzles (Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 53570/1980 and the like.).
(3) With a cap placed closely to the points of the nozzles, the bubbles, foreign matter, etc., are sucked up along with the ink by a suction pump from the nozzles (Japanese Patent O.P.I. Publication No. 113464/1981).
However, the above procedures for purging bubbles and foreign matter have the following disadvantages which have been in question in the practical application.
The way of mechanically pressing the tank of (1) is lacking in the pressure accuracy as well as in the pressure stability, particularly it is difficult to apply a given constant pressure regardless of the residual quantity of the ink in the tank.
The pressurizing way by use of a pressure pump of (2) requires an expensive pump for liquid use, so that it becomes a problem in respect of cost.
The way of sucking from the points of the nozzles of (3) requires a complex and expensive apparatus and also requires a high accuracy due to the mutual relation between the sucking rate and the ink supply rate.
As described above, any of the conventional purging means is insufficient with respect to the structure, cost and stabilty thereof.
On the other hand, in the ink jet recording apparatus, as the ink supply means to supply ink to the recording head, there is usually used an airtight ink cartridge to keep the ink stable from air. The ink cartridge comprises a highly hermetically sealed bag or container containing ink. This ink cartridge is provided attachably and detachably in a cartridge receiving position, and the replacement of the cartridge enables the replenishment of new ink.